Radioactive fucose was injected into the vitreous chambers of the eyes of normal beagles as well as the eyes of miniature poodles, a breed of dog that can be affected with inherited progressive rod-cone degeneration. In beagles the fucose was incorporated into an integral membrane protein having the properties of opsin on SDS gel electrophoresis. Autoradiography of poodle retinas revealed a labeled band in the rod outer segments characteristic of labeled rhodopsin. Heretofore fucose was thought to label only cone visual pigments.